This invention relates to a stepping motor widely used as a drive source for office automation equipment, various kinds of automatic production units or the like, and more particularly to an inertial damper structure for a stepping motor which is adapted to converge vibration of the stepping motor and reduce instability of the stepping motor during the step response of the stepping motor.
A stepping motor exhibits excellent functions such as accurate driving, rapid stopping, rapid starting and the like. On the other hand, it has disadvantages in that the transient response during acceleration at the time of starting of rotation is apt to be vibratory, and unstable phenomena such as resonance in a fixed frequency domain of a drive power supply and the like fail to permit the rotation of the motor to be smoothly carried out. Accordingly, in order to properly drive equipment by means of the stepping motor, a mechanism for eliminating such disadvantages as described above is necessarily required. In view of the foregoing, the inventor developed an inertia damper utilizing a gel material while taking notice of the fact that it exhibits good vibration absorbing characteristics. The proposed inertia damper generally includes a mount base, an inertia weight element and a gel element, wherein the mount base and inertia weight element are coupled to each other through the gel element in a vibration absorbing manner and the mount base is mounted on an output shaft of a motor.
Now, an inertia damper of this type which is currently used will be described hereinafter with reference to FIG. 1. The inertia damper includes a mount base 100, an inertia weight component or element 102 and a gel material or element 104 and is constructed in such a manner that the mount base 100 and inertia weight element 102 are connected to each other in a vibration absorbing manner through the gel element 104 arranged between the inner peripheral surface of the inertia weight element 102 formed into an annular shape and a boss 106 of the mount base 100. Thus, in the conventional inertia damper constructed as described above, a space in which the gel element 104 is arranged is of relatively small dimensions, so that the gel element 104 may very satisfactorily absorb vibration of a small magnitude. However, such construction fails to cause the gel element 104 to satisfactory absorb vibration of a large magnitude, as well as exhibit good endurance under the operating conditions that a large amount of vibration energy is applied thereto.
Also, the inertia damper is conventionally mounted as a separate element on the stepping motor, therefore, it is required to provide the motor with a mounting shaft extending from one side of the motor in one direction for mounting the inertia damper on the motor therethrough as well as an output shaft in the opposite direction. However, in order to prevent the structure of the stepping motor from being complicated, it is desired to eliminate such a mounting shaft as described above. Thus, it is desirable to provide a stepping motor which is provided with an inertia damper in a manner to be incorporated in the stepping motor rather than as a separate element.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a stepping motor which is capable itself of exhibiting a function of an inertia damper.
It is another object of the present invention to provide a stepping motor which is capable of improving responsiveness and the elimination of instability during operation.
It is a further object of the present invention to provide a stepping motor which is capable of exhibiting satisfactory endurance under various operating conditions.
It is still another object of the present invention to provide a stepping motor which is capable of exhibiting excellent characteristics while remaining compact in size.
It is yet another object of the present invention to provide a stepping motor which is easily assembled and which has an uncomplicated structure.
It is a still further object of the present invention to provide a stepping motor which is capable of exhibiting satisfactory performance while keeping the structure significantly compact.
In accordance with one aspect of the present invention, a stepping motor is provided. The stepping motor comprises a casing, an output shaft arranged so as to extend outwardly from the casing, a rotor arranged in the casing and connected to the output shaft in the casing, and a stator substantially stationarily arranged in the casing and including at least one stator core and an excitation coil. The stepping motor also includes a gel element which is arranged in at least one of at least a part of a space defined between the casing and the stator and at least a part of a space defined between the output shaft and the rotor.
In the present invention, the construction in which the gel element is arranged in at least a part of the space between the casing and the stator is such that the gel element may be pro-vided in the entire space between the casing and the stator or a part of the space. Alternatively, the gel element may be arranged in at least a part of a space(s) between or in components for constituting at least one of the casing and the stator. Also, the construction in which the gel element is arranged in at least a part of the space between the output shaft and the rotor is such that the gel element may be arranged in the entire space between the output shaft and the rotor or a part of the space. Alternatively, the gel element may be arranged in at least a part of a space(s) between or in components for constituting at least one of the output shaft and the rotor.
In the present invention, the gel element may be directly or indirectly arranged. In the present invention, the construction in which the gel element is directly arranged is such that it is arranged without using any interstitial or intermediate member or element and the construction in which the gel element is indirectly arranged is such that it is arranged through an interstitial or intermediate member or element.
The stepping motor of the present invention constructed as described above permits the gel element to function to absorb vibration, such that in the stepping motor exhibits characteristics of an inertial damper.